sequence diagram message connector

[Jie_Zhao]

Hi,

I tried to model a scenario as follows in a sequence diagram:
class CalcController
{
  ...
 public void Start()
  {
      this.Calculate();
  }
  public void Calculate()
  {
      calculatorObj.CalculateCase();
  }
  ...
}

The Calculate method above is modeled as a self-message and with"Extend Method Invocation" option checked, the problem I had was to embed message CalculateCase into the Calculate method.

Thanks a lot in advance.

Jie